grab from latest android

git-svn-id: http://skia.googlecode.com/svn/trunk@27 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 978 insertions, 0 deletions

diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
new file mode 100644
index 0000000000..e8a202dc08
--- /dev/null
+++ b/src/core/SkXfermode.cpp
@@ -0,0 +1,978 @@
+/*
+ * Copyright (C) 2006 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "SkXfermode.h"
+#include "SkColorPriv.h"
+
+#define SkAlphaMulAlpha(a, b)   SkMulDiv255Round(a, b)
+
+static SkPMColor SkFourByteInterp(SkPMColor src, SkPMColor dst, U8CPU alpha) {
+    unsigned scale = SkAlpha255To256(alpha);
+
+    unsigned a = SkAlphaBlend(SkGetPackedA32(src), SkGetPackedA32(dst), scale);
+    unsigned r = SkAlphaBlend(SkGetPackedR32(src), SkGetPackedR32(dst), scale);
+    unsigned g = SkAlphaBlend(SkGetPackedG32(src), SkGetPackedG32(dst), scale);
+    unsigned b = SkAlphaBlend(SkGetPackedB32(src), SkGetPackedB32(dst), scale);
+
+    return SkPackARGB32(a, r, g, b);
+}
+
+// idea for higher precision blends in xfer procs (and slightly faster)
+// see DstATop as a probable caller
+static U8CPU mulmuldiv255round(U8CPU a, U8CPU b, U8CPU c, U8CPU d) {
+    SkASSERT(a <= 255);
+    SkASSERT(b <= 255);
+    SkASSERT(c <= 255);
+    SkASSERT(d <= 255);
+    unsigned prod = SkMulS16(a, b) + SkMulS16(c, d) + 128;
+    unsigned result = (prod + (prod >> 8)) >> 8;
+    SkASSERT(result <= 255);
+    return result;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+bool SkXfermode::asCoeff(Coeff* src, Coeff* dst) {
+    return false;
+}
+
+SkPMColor SkXfermode::xferColor(SkPMColor src, SkPMColor dst) {
+    // no-op. subclasses should override this
+    return dst;
+}
+
+void SkXfermode::xfer32(SK_RESTRICT SkPMColor dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+
+    if (NULL == aa) {
+        for (int i = count - 1; i >= 0; --i) {
+            dst[i] = this->xferColor(src[i], dst[i]);
+        }
+    } else {
+        for (int i = count - 1; i >= 0; --i) {
+            unsigned a = aa[i];
+            if (0 != a) {
+                SkPMColor dstC = dst[i];
+                SkPMColor C = this->xferColor(src[i], dstC);
+                if (0xFF != a) {
+                    C = SkFourByteInterp(C, dstC, a);
+                }
+                dst[i] = C;
+            }
+        }
+    }
+}
+
+void SkXfermode::xfer16(SK_RESTRICT uint16_t dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+
+    if (NULL == aa) {
+        for (int i = count - 1; i >= 0; --i) {
+            SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+            dst[i] = SkPixel32ToPixel16_ToU16(this->xferColor(src[i], dstC));
+        }
+    } else {
+        for (int i = count - 1; i >= 0; --i) {
+            unsigned a = aa[i];
+            if (0 != a) {
+                SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+                SkPMColor C = this->xferColor(src[i], dstC);
+                if (0xFF != a) {
+                    C = SkFourByteInterp(C, dstC, a);
+                }
+                dst[i] = SkPixel32ToPixel16_ToU16(C);
+            }
+        }
+    }
+}
+
+void SkXfermode::xfer4444(SK_RESTRICT SkPMColor16 dst[],
+                          const SK_RESTRICT SkPMColor src[], int count,
+                          const SK_RESTRICT SkAlpha aa[])
+{
+    SkASSERT(dst && src && count >= 0);
+    
+    if (NULL == aa) {
+        for (int i = count - 1; i >= 0; --i) {
+            SkPMColor dstC = SkPixel4444ToPixel32(dst[i]);
+            dst[i] = SkPixel32ToPixel4444(this->xferColor(src[i], dstC));
+        }
+    } else {
+        for (int i = count - 1; i >= 0; --i) {
+            unsigned a = aa[i];
+            if (0 != a) {
+                SkPMColor dstC = SkPixel4444ToPixel32(dst[i]);
+                SkPMColor C = this->xferColor(src[i], dstC);
+                if (0xFF != a) {
+                    C = SkFourByteInterp(C, dstC, a);
+                }
+                dst[i] = SkPixel32ToPixel4444(C);
+            }
+        }
+    }
+}
+
+void SkXfermode::xferA8(SK_RESTRICT SkAlpha dst[],
+                        const SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[])
+{
+    SkASSERT(dst && src && count >= 0);
+
+    if (NULL == aa) {
+        for (int i = count - 1; i >= 0; --i) {
+            SkPMColor res = this->xferColor(src[i], (dst[i] << SK_A32_SHIFT));
+            dst[i] = SkToU8(SkGetPackedA32(res));
+        }
+    } else {
+        for (int i = count - 1; i >= 0; --i) {
+            unsigned a = aa[i];
+            if (0 != a) {
+                SkAlpha dstA = dst[i];
+                unsigned A = SkGetPackedA32(this->xferColor(src[i],
+                                            (SkPMColor)(dstA << SK_A32_SHIFT)));
+                if (0xFF != a) {
+                    A = SkAlphaBlend(A, dstA, SkAlpha255To256(a));
+                }
+                dst[i] = SkToU8(A);
+            }
+        }
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+void SkProcXfermode::xfer32(SK_RESTRICT SkPMColor dst[],
+                            const SK_RESTRICT SkPMColor src[], int count,
+                            const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+
+    SkXfermodeProc proc = fProc;
+
+    if (NULL != proc) {
+        if (NULL == aa) {
+            for (int i = count - 1; i >= 0; --i) {
+                dst[i] = proc(src[i], dst[i]);
+            }
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0 != a) {
+                    SkPMColor dstC = dst[i];
+                    SkPMColor C = proc(src[i], dstC);
+                    if (a != 0xFF) {
+                        C = SkFourByteInterp(C, dstC, a);
+                    }
+                    dst[i] = C;
+                }
+            }
+        }
+    }
+}
+
+void SkProcXfermode::xfer16(SK_RESTRICT uint16_t dst[],
+                            const SK_RESTRICT SkPMColor src[], int count,
+                            const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+
+    SkXfermodeProc proc = fProc;
+
+    if (NULL != proc) {
+        if (NULL == aa) {
+            for (int i = count - 1; i >= 0; --i) {
+                SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+                dst[i] = SkPixel32ToPixel16_ToU16(proc(src[i], dstC));
+            }
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0 != a) {
+                    SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
+                    SkPMColor C = proc(src[i], dstC);
+                    if (0xFF != a) {
+                        C = SkFourByteInterp(C, dstC, a);
+                    }
+                    dst[i] = SkPixel32ToPixel16_ToU16(C);
+                }
+            }
+        }
+    }
+}
+
+void SkProcXfermode::xfer4444(SK_RESTRICT SkPMColor16 dst[],
+                              const SK_RESTRICT SkPMColor src[], int count,
+                              const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+    
+    SkXfermodeProc proc = fProc;
+
+    if (NULL != proc) {
+        if (NULL == aa) {
+            for (int i = count - 1; i >= 0; --i) {
+                SkPMColor dstC = SkPixel4444ToPixel32(dst[i]);
+                dst[i] = SkPixel32ToPixel4444(proc(src[i], dstC));
+            }
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0 != a) {
+                    SkPMColor dstC = SkPixel4444ToPixel32(dst[i]);
+                    SkPMColor C = proc(src[i], dstC);
+                    if (0xFF != a) {
+                        C = SkFourByteInterp(C, dstC, a);
+                    }
+                    dst[i] = SkPixel32ToPixel4444(C);
+                }
+            }
+        }
+    }
+}
+
+void SkProcXfermode::xferA8(SK_RESTRICT SkAlpha dst[],
+                            const SK_RESTRICT SkPMColor src[], int count,
+                            const SK_RESTRICT SkAlpha aa[]) {
+    SkASSERT(dst && src && count >= 0);
+
+    SkXfermodeProc proc = fProc;
+
+    if (NULL != proc) {
+        if (NULL == aa) {
+            for (int i = count - 1; i >= 0; --i) {
+                SkPMColor res = proc(src[i], dst[i] << SK_A32_SHIFT);
+                dst[i] = SkToU8(SkGetPackedA32(res));
+            }
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0 != a) {
+                    SkAlpha dstA = dst[i];
+                    SkPMColor res = proc(src[i], dstA << SK_A32_SHIFT);
+                    unsigned A = SkGetPackedA32(res);
+                    if (0xFF != a) {
+                        A = SkAlphaBlend(A, dstA, SkAlpha255To256(a));
+                    }
+                    dst[i] = SkToU8(A);
+                }
+            }
+        }
+    }
+}
+
+SkProcXfermode::SkProcXfermode(SkFlattenableReadBuffer& buffer)
+        : SkXfermode(buffer) {
+    fProc = (SkXfermodeProc)buffer.readFunctionPtr();
+}
+
+void SkProcXfermode::flatten(SkFlattenableWriteBuffer& buffer) {
+    buffer.writeFunctionPtr((void*)fProc);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+///////////////////////////////////////////////////////////////////////////////
+
+class SkProcCoeffXfermode : public SkProcXfermode {
+public:
+    SkProcCoeffXfermode(SkXfermodeProc proc, Coeff sc, Coeff dc)
+            : INHERITED(proc), fSrcCoeff(sc), fDstCoeff(dc) {
+    }
+    
+    virtual bool asCoeff(Coeff* sc, Coeff* dc) {
+        if (sc) {
+            *sc = fSrcCoeff;
+        }
+        if (dc) {
+            *dc = fDstCoeff;
+        }
+        return true;
+    }
+    
+    virtual Factory getFactory() { return CreateProc; }
+    virtual void flatten(SkFlattenableWriteBuffer& buffer) {
+        this->INHERITED::flatten(buffer);
+        buffer.write32(fSrcCoeff);
+        buffer.write32(fDstCoeff);
+    }
+
+protected:
+    SkProcCoeffXfermode(SkFlattenableReadBuffer& buffer)
+            : INHERITED(buffer) {
+        fSrcCoeff = (Coeff)buffer.readU32();
+        fDstCoeff = (Coeff)buffer.readU32();
+    }
+    
+private:
+    Coeff   fSrcCoeff, fDstCoeff;
+    
+    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
+    return SkNEW_ARGS(SkProcCoeffXfermode, (buffer)); }
+
+    typedef SkProcXfermode INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+//  kClear_Mode,    //!< [0, 0]
+static SkPMColor clear_modeproc(SkPMColor src, SkPMColor dst) {
+    return 0;
+}
+
+//  kSrc_Mode,      //!< [Sa, Sc]
+static SkPMColor src_modeproc(SkPMColor src, SkPMColor dst) {
+    return src;
+}
+
+//  kDst_Mode,      //!< [Da, Dc]
+static SkPMColor dst_modeproc(SkPMColor src, SkPMColor dst) {
+    return dst;
+}
+
+//  kSrcOver_Mode,  //!< [Sa + (1 - Sa)*Da, Sc + (1 - Sa)*Dc] 
+static SkPMColor srcover_modeproc(SkPMColor src, SkPMColor dst) {
+    return src + SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
+}
+
+//  kDstOver_Mode,  //!< [Sa + (1 - Sa)*Da, Dc + (1 - Da)*Sc]
+static SkPMColor dstover_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned ida = 255 - da;
+    
+    return SkPackARGB32(sa + da - SkAlphaMulAlpha(sa, da),
+        SkGetPackedR32(dst) + SkAlphaMulAlpha(ida, SkGetPackedR32(src)),
+        SkGetPackedG32(dst) + SkAlphaMulAlpha(ida, SkGetPackedG32(src)),
+        SkGetPackedB32(dst) + SkAlphaMulAlpha(ida, SkGetPackedB32(src)));
+}
+
+//  kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]
+static SkPMColor srcin_modeproc(SkPMColor src, SkPMColor dst) {
+    return SkAlphaMulQ(src, SkAlpha255To256(SkGetPackedA32(dst)));
+}
+
+//  kDstIn_Mode,    //!< [Sa * Da, Sa * Dc]
+static SkPMColor dstin_modeproc(SkPMColor src, SkPMColor dst) {
+    return SkAlphaMulQ(dst, SkAlpha255To256(SkGetPackedA32(src)));
+}
+
+//  kSrcOut_Mode,   //!< [Sa * (1 - Da), Sc * (1 - Da)]
+static SkPMColor srcout_modeproc(SkPMColor src, SkPMColor dst) {
+    return SkAlphaMulQ(src, SkAlpha255To256(255 - SkGetPackedA32(dst)));
+}
+
+//  kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]
+static SkPMColor dstout_modeproc(SkPMColor src, SkPMColor dst) {
+    return SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
+}
+
+//  kSrcATop_Mode,  //!< [Da, Sc * Da + (1 - Sa) * Dc]
+static SkPMColor srcatop_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned isa = 255 - sa;
+
+    return SkPackARGB32(da,
+                        SkAlphaMulAlpha(da, SkGetPackedR32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedR32(dst)),
+                        SkAlphaMulAlpha(da, SkGetPackedG32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedG32(dst)),
+                        SkAlphaMulAlpha(da, SkGetPackedB32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedB32(dst)));
+}
+
+//  kDstATop_Mode,  //!< [Sa, Sa * Dc + Sc * (1 - Da)]
+static SkPMColor dstatop_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned ida = 255 - da;
+
+    return SkPackARGB32(sa,
+                        SkAlphaMulAlpha(ida, SkGetPackedR32(src)) +
+                            SkAlphaMulAlpha(sa, SkGetPackedR32(dst)),
+                        SkAlphaMulAlpha(ida, SkGetPackedG32(src)) +
+                            SkAlphaMulAlpha(sa, SkGetPackedG32(dst)),
+                        SkAlphaMulAlpha(ida, SkGetPackedB32(src)) +
+                            SkAlphaMulAlpha(sa, SkGetPackedB32(dst)));
+}
+
+//  kXor_Mode   [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]
+static SkPMColor xor_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned isa = 255 - sa;
+    unsigned ida = 255 - da;
+
+    return SkPackARGB32(sa + da - (SkAlphaMulAlpha(sa, da) << 1),
+                        SkAlphaMulAlpha(ida, SkGetPackedR32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedR32(dst)),
+                        SkAlphaMulAlpha(ida, SkGetPackedG32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedG32(dst)),
+                        SkAlphaMulAlpha(ida, SkGetPackedB32(src)) +
+                            SkAlphaMulAlpha(isa, SkGetPackedB32(dst)));
+}
+
+
+// kDarken_Mode,   [Sa + Da - Sa·Da, Sc·(1 - Da) + Dc·(1 - Sa) + min(Sc, Dc)]
+
+static inline unsigned darken_p(unsigned src, unsigned dst,
+                                unsigned src_mul, unsigned dst_mul) {
+    return ((dst_mul * src + src_mul * dst) >> 8) + SkMin32(src, dst);
+}
+
+static SkPMColor darken_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned src_scale = SkAlpha255To256(255 - sa);
+    unsigned dst_scale = SkAlpha255To256(255 - da);
+
+    unsigned ra = sa + da - SkAlphaMulAlpha(sa, da);
+    unsigned rr = darken_p(SkGetPackedR32(src), SkGetPackedR32(dst),
+                           src_scale, dst_scale);
+    unsigned rg = darken_p(SkGetPackedG32(src), SkGetPackedG32(dst),
+                           src_scale, dst_scale);
+    unsigned rb = darken_p(SkGetPackedB32(src), SkGetPackedB32(dst),
+                           src_scale, dst_scale);
+
+    return SkPackARGB32(ra, SkFastMin32(rr, ra),
+                        SkFastMin32(rg, ra), SkFastMin32(rb, ra));
+}
+
+// kLighten_Mode,  [Sa + Da - Sa·Da, Sc·(1 - Da) + Dc·(1 - Sa) + max(Sc, Dc)]
+static inline unsigned lighten_p(unsigned src, unsigned dst,
+                                 unsigned src_mul, unsigned dst_mul) {
+    return ((dst_mul * src + src_mul * dst) >> 8) + SkMax32(src, dst);
+}
+
+static SkPMColor lighten_modeproc(SkPMColor src, SkPMColor dst) {
+    unsigned sa = SkGetPackedA32(src);
+    unsigned da = SkGetPackedA32(dst);
+    unsigned src_scale = SkAlpha255To256(255 - sa);
+    unsigned dst_scale = SkAlpha255To256(255 - da);
+    
+    unsigned ra = sa + da - SkAlphaMulAlpha(sa, da);
+    unsigned rr = lighten_p(SkGetPackedR32(src), SkGetPackedR32(dst),
+                            src_scale, dst_scale);
+    unsigned rg = lighten_p(SkGetPackedG32(src), SkGetPackedG32(dst),
+                            src_scale, dst_scale);
+    unsigned rb = lighten_p(SkGetPackedB32(src), SkGetPackedB32(dst),
+                            src_scale, dst_scale);
+
+    return SkPackARGB32(ra, SkFastMin32(rr, ra),
+                        SkFastMin32(rg, ra), SkFastMin32(rb, ra));
+}
+    
+static SkPMColor mult_modeproc(SkPMColor src, SkPMColor dst) {
+    int a = SkAlphaMulAlpha(SkGetPackedA32(src), SkGetPackedA32(dst));
+    int r = SkAlphaMulAlpha(SkGetPackedR32(src), SkGetPackedR32(dst));
+    int g = SkAlphaMulAlpha(SkGetPackedG32(src), SkGetPackedG32(dst));
+    int b = SkAlphaMulAlpha(SkGetPackedB32(src), SkGetPackedB32(dst));
+    return SkPackARGB32(a, r, g, b);
+}
+
+static inline int screen_byte(int a, int b) {
+    return a + b - SkAlphaMulAlpha(a, b);
+}
+
+static SkPMColor screen_modeproc(SkPMColor src, SkPMColor dst) {
+    int a = screen_byte(SkGetPackedA32(src), SkGetPackedA32(dst));
+    int r = screen_byte(SkGetPackedR32(src), SkGetPackedR32(dst));
+    int g = screen_byte(SkGetPackedG32(src), SkGetPackedG32(dst));
+    int b = screen_byte(SkGetPackedB32(src), SkGetPackedB32(dst));
+    return SkPackARGB32(a, r, g, b);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+class SkClearXfermode : public SkProcCoeffXfermode {
+public:
+    SkClearXfermode() : SkProcCoeffXfermode(clear_modeproc,
+                                            kZero_Coeff, kZero_Coeff) {}
+
+    virtual void xfer32(SK_RESTRICT SkPMColor dst[],
+                        const SK_RESTRICT SkPMColor[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && count >= 0);
+
+        if (NULL == aa) {
+            memset(dst, 0, count << 2);
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0xFF == a) {
+                    dst[i] = 0;
+                } else if (a != 0) {
+                    dst[i] = SkAlphaMulQ(dst[i], SkAlpha255To256(255 - a));
+                }
+            }
+        }
+    }
+    virtual void xferA8(SK_RESTRICT SkAlpha dst[],
+                        const SK_RESTRICT SkPMColor[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && count >= 0);
+
+        if (NULL == aa) {
+            memset(dst, 0, count);
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0xFF == a) {
+                    dst[i] = 0;
+                } else if (0 != a) {
+                    dst[i] = SkAlphaMulAlpha(dst[i], 255 - a);
+                }
+            }
+        }
+    }
+    
+    virtual Factory getFactory() { return CreateProc; }
+
+private:
+    SkClearXfermode(SkFlattenableReadBuffer& buffer)
+        : SkProcCoeffXfermode(buffer) {}
+    
+    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
+        return SkNEW_ARGS(SkClearXfermode, (buffer));
+    }
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+class SkSrcXfermode : public SkProcCoeffXfermode {
+public:
+    SkSrcXfermode() : SkProcCoeffXfermode(src_modeproc,
+                                          kOne_Coeff, kZero_Coeff) {}
+
+    virtual void xfer32(SK_RESTRICT SkPMColor dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && src && count >= 0);
+
+        if (NULL == aa) {
+            memcpy(dst, src, count << 2);
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (a == 0xFF) {
+                    dst[i] = src[i];
+                } else if (a != 0) {
+                    dst[i] = SkFourByteInterp(src[i], dst[i], a);
+                }
+            }
+        }
+    }
+
+    virtual void xferA8(SK_RESTRICT SkAlpha dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && src && count >= 0);
+
+        if (NULL == aa) {
+            for (int i = count - 1; i >= 0; --i) {
+                dst[i] = SkToU8(SkGetPackedA32(src[i]));
+            }
+        } else {
+            for (int i = count - 1; i >= 0; --i) {
+                unsigned a = aa[i];
+                if (0 != a) {
+                    unsigned srcA = SkGetPackedA32(src[i]);
+                    if (a == 0xFF) {
+                        dst[i] = SkToU8(srcA);
+                    } else {
+                        dst[i] = SkToU8(SkAlphaBlend(srcA, dst[i], a));
+                    }
+                }
+            }
+        }
+    }
+    
+    virtual Factory getFactory() { return CreateProc; }
+
+private:
+    SkSrcXfermode(SkFlattenableReadBuffer& buffer)
+        : SkProcCoeffXfermode(buffer) {}
+    
+    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
+        return SkNEW_ARGS(SkSrcXfermode, (buffer));
+    }
+};
+
+class SkDstInXfermode : public SkProcCoeffXfermode {
+public:
+    SkDstInXfermode() : SkProcCoeffXfermode(dstin_modeproc,
+                                            kZero_Coeff, kSA_Coeff) {}
+    
+    virtual void xfer32(SK_RESTRICT SkPMColor dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && src);
+        
+        if (count <= 0) {
+            return;
+        }
+        if (NULL != aa) {
+            return this->INHERITED::xfer32(dst, src, count, aa);
+        }
+        
+        do {
+            unsigned a = SkGetPackedA32(*src);
+            *dst = SkAlphaMulQ(*dst, SkAlpha255To256(a));
+            dst++;
+            src++;
+        } while (--count != 0);
+    }
+    
+    virtual Factory getFactory() { return CreateProc; }
+    
+private:
+    SkDstInXfermode(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
+    
+    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
+        return SkNEW_ARGS(SkDstInXfermode, (buffer));
+    }
+    
+    typedef SkProcCoeffXfermode INHERITED;
+};
+
+class SkDstOutXfermode : public SkProcCoeffXfermode {
+public:
+    SkDstOutXfermode() : SkProcCoeffXfermode(dstout_modeproc,
+                                             kZero_Coeff, kISA_Coeff) {}
+    
+    virtual void xfer32(SK_RESTRICT SkPMColor dst[],
+                        const SK_RESTRICT SkPMColor src[], int count,
+                        const SK_RESTRICT SkAlpha aa[]) {
+        SkASSERT(dst && src);
+        
+        if (count <= 0) {
+            return;
+        }
+        if (NULL != aa) {
+            return this->INHERITED::xfer32(dst, src, count, aa);
+        }
+        
+        do {
+            unsigned a = SkGetPackedA32(*src);
+            *dst = SkAlphaMulQ(*dst, SkAlpha255To256(255 - a));
+            dst++;
+            src++;
+        } while (--count != 0);
+    }
+    
+    virtual Factory getFactory() { return CreateProc; }
+    
+private:
+    SkDstOutXfermode(SkFlattenableReadBuffer& buffer)
+        : INHERITED(buffer) {}
+    
+    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
+        return SkNEW_ARGS(SkDstOutXfermode, (buffer));
+    }
+    
+    typedef SkProcCoeffXfermode INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+#include "SkPorterDuff.h"
+
+struct ProcCoeff {
+    SkXfermodeProc      fProc;
+    SkXfermode::Coeff   fSC;
+    SkXfermode::Coeff   fDC;
+};
+
+static const ProcCoeff gProcCoeffs[] = {
+    { clear_modeproc,   SkXfermode::kZero_Coeff,    SkXfermode::kZero_Coeff },
+    { src_modeproc,     SkXfermode::kOne_Coeff,     SkXfermode::kZero_Coeff },
+    { dst_modeproc,     SkXfermode::kZero_Coeff,    SkXfermode::kOne_Coeff },
+    { srcover_modeproc, SkXfermode::kOne_Coeff,     SkXfermode::kISA_Coeff },
+    { dstover_modeproc, SkXfermode::kIDA_Coeff,     SkXfermode::kOne_Coeff },
+    { srcin_modeproc,   SkXfermode::kDA_Coeff,      SkXfermode::kZero_Coeff },
+    { dstin_modeproc,   SkXfermode::kZero_Coeff,    SkXfermode::kSA_Coeff },
+    { srcout_modeproc,  SkXfermode::kIDA_Coeff,     SkXfermode::kZero_Coeff },
+    { dstout_modeproc,  SkXfermode::kZero_Coeff,    SkXfermode::kISA_Coeff },
+    { srcatop_modeproc, SkXfermode::kDA_Coeff,      SkXfermode::kISA_Coeff },
+    { dstatop_modeproc, SkXfermode::kIDA_Coeff,     SkXfermode::kSA_Coeff },
+    { xor_modeproc,     SkXfermode::kIDA_Coeff,     SkXfermode::kISA_Coeff },
+    // these two can't be represented as coefficients
+    { darken_modeproc,  SkXfermode::Coeff(-1),      SkXfermode::Coeff(-1) },
+    { lighten_modeproc, SkXfermode::Coeff(-1),      SkXfermode::Coeff(-1) },
+    // these can use coefficients
+    { mult_modeproc,    SkXfermode::kZero_Coeff,    SkXfermode::kSC_Coeff },
+    { screen_modeproc,  SkXfermode::kOne_Coeff,     SkXfermode::kISC_Coeff }
+};
+
+SkXfermode* SkPorterDuff::CreateXfermode(SkPorterDuff::Mode mode) {
+    SkASSERT(SK_ARRAY_COUNT(gProcCoeffs) == SkPorterDuff::kModeCount);
+    SkASSERT((unsigned)mode < SkPorterDuff::kModeCount);
+
+    switch (mode) {
+        case kClear_Mode:
+            return SkNEW(SkClearXfermode);
+        case kSrc_Mode:
+            return SkNEW(SkSrcXfermode);
+        case kSrcOver_Mode:
+            return NULL;
+        case kDstIn_Mode:
+            return SkNEW(SkDstInXfermode);
+        case kDstOut_Mode:
+            return SkNEW(SkDstOutXfermode);
+        // these two can't be represented with Coeff
+        case kDarken_Mode:
+            return SkNEW_ARGS(SkProcXfermode, (darken_modeproc));
+        case kLighten_Mode:
+            return SkNEW_ARGS(SkProcXfermode, (lighten_modeproc));
+        // use the table 
+        default: {
+            const ProcCoeff& rec = gProcCoeffs[mode];
+            SkASSERT((unsigned)rec.fSC < SkXfermode::kCoeffCount);
+            SkASSERT((unsigned)rec.fDC < SkXfermode::kCoeffCount);
+            return SkNEW_ARGS(SkProcCoeffXfermode, (rec.fProc,
+                                                    rec.fSC, rec.fDC));
+        }
+    }
+}
+
+bool SkPorterDuff::IsMode(SkXfermode* xfer, Mode* mode) {
+    if (NULL == xfer) {
+        if (mode) {
+            *mode = kSrcOver_Mode;
+        }
+        return true;
+    }
+
+    SkXfermode::Coeff sc, dc;
+    if (xfer->asCoeff(&sc, &dc)) {
+        SkASSERT((unsigned)sc < (unsigned)SkXfermode::kCoeffCount);
+        SkASSERT((unsigned)dc < (unsigned)SkXfermode::kCoeffCount);
+        
+        const ProcCoeff* rec = gProcCoeffs;
+        for (size_t i = 0; i < SK_ARRAY_COUNT(gProcCoeffs); i++) {
+            if (rec[i].fSC == sc && rec[i].fDC == dc) {
+                if (mode) {
+                    *mode = SkPorterDuff::Mode(i);
+                }
+                return true;
+            }
+        }
+    }
+
+    // no coefficients, or not found in our table
+    return false;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+#ifdef SK_DEBUG
+static void unit_test() {
+    for (unsigned a = 0; a <= 255; a++) {
+        for (unsigned c = 0; c <= a; c++) {
+            SkPMColor pm = SkPackARGB32(a, c, c, c);
+            for (unsigned aa = 0; aa <= 255; aa++) {
+                for (unsigned cc = 0; cc <= aa; cc++) {
+                    SkPMColor pm2 = SkPackARGB32(aa, cc, cc, cc);
+                    
+                    const size_t N = SK_ARRAY_COUNT(gProcCoeffs);
+                    for (size_t i = 0; i < N; i++) {
+                        gProcCoeffs[i].fProc(pm, pm2);
+                    }
+                }
+            }
+        }
+    }            
+}
+#endif
+
+SkXfermodeProc SkPorterDuff::GetXfermodeProc(Mode mode) {
+#ifdef SK_DEBUGx
+    static bool gUnitTest;
+    if (!gUnitTest) {
+        gUnitTest = true;
+        unit_test();
+    }
+#endif
+
+    SkXfermodeProc  proc = NULL;
+
+    if ((unsigned)mode < SkPorterDuff::kModeCount) {
+        proc = gProcCoeffs[mode].fProc;
+    }
+    return proc;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//////////// 16bit xfermode procs
+
+#ifdef SK_DEBUG
+static bool require_255(SkPMColor src) { return SkGetPackedA32(src) == 0xFF; }
+static bool require_0(SkPMColor src) { return SkGetPackedA32(src) == 0; }
+#endif
+
+static uint16_t src_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return SkPixel32ToPixel16(src);
+}
+
+static uint16_t dst_modeproc16(SkPMColor src, uint16_t dst) {
+    return dst;
+}
+
+static uint16_t srcover_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return dst;
+}
+
+static uint16_t srcover_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return SkPixel32ToPixel16(src);
+}
+
+static uint16_t dstover_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return dst;
+}
+
+static uint16_t dstover_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return dst;
+}
+
+static uint16_t srcin_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return SkPixel32ToPixel16(src);
+}
+
+static uint16_t dstin_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return dst;
+}
+
+static uint16_t dstout_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return dst;
+}
+
+static uint16_t srcatop_modeproc16(SkPMColor src, uint16_t dst) {
+    unsigned isa = 255 - SkGetPackedA32(src);
+    
+    return SkPackRGB16(
+           SkPacked32ToR16(src) + SkAlphaMulAlpha(SkGetPackedR16(dst), isa),
+           SkPacked32ToG16(src) + SkAlphaMulAlpha(SkGetPackedG16(dst), isa),
+           SkPacked32ToB16(src) + SkAlphaMulAlpha(SkGetPackedB16(dst), isa));
+}
+
+static uint16_t srcatop_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return dst;
+}
+
+static uint16_t srcatop_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return SkPixel32ToPixel16(src);
+}
+
+static uint16_t dstatop_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    return dst;
+}
+
+/*********
+    darken and lighten boil down to this.
+
+    darken  = (1 - Sa) * Dc + min(Sc, Dc)
+    lighten = (1 - Sa) * Dc + max(Sc, Dc)
+
+    if (Sa == 0) these become
+        darken  = Dc + min(0, Dc) = 0
+        lighten = Dc + max(0, Dc) = Dc
+
+    if (Sa == 1) these become
+        darken  = min(Sc, Dc)
+        lighten = max(Sc, Dc)
+*/
+
+static uint16_t darken_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return 0;
+}
+
+static uint16_t darken_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    unsigned r = SkFastMin32(SkPacked32ToR16(src), SkGetPackedR16(dst));
+    unsigned g = SkFastMin32(SkPacked32ToG16(src), SkGetPackedG16(dst));
+    unsigned b = SkFastMin32(SkPacked32ToB16(src), SkGetPackedB16(dst));
+    return SkPackRGB16(r, g, b);
+}
+
+static uint16_t lighten_modeproc16_0(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_0(src));
+    return dst;
+}
+
+static uint16_t lighten_modeproc16_255(SkPMColor src, uint16_t dst) {
+    SkASSERT(require_255(src));
+    unsigned r = SkMax32(SkPacked32ToR16(src), SkGetPackedR16(dst));
+    unsigned g = SkMax32(SkPacked32ToG16(src), SkGetPackedG16(dst));
+    unsigned b = SkMax32(SkPacked32ToB16(src), SkGetPackedB16(dst));
+    return SkPackRGB16(r, g, b);
+}
+
+struct Proc16Rec {
+    SkXfermodeProc16    fProc16_0;
+    SkXfermodeProc16    fProc16_255;
+    SkXfermodeProc16    fProc16_General;
+};
+
+static const Proc16Rec gPorterDuffModeProcs16[] = {
+    { NULL,                 NULL,                   NULL            }, // CLEAR
+    { NULL,                 src_modeproc16_255,     NULL            },
+    { dst_modeproc16,       dst_modeproc16,         dst_modeproc16  },
+    { srcover_modeproc16_0, srcover_modeproc16_255, NULL            },
+    { dstover_modeproc16_0, dstover_modeproc16_255, NULL            },
+    { NULL,                 srcin_modeproc16_255,   NULL            },
+    { NULL,                 dstin_modeproc16_255,   NULL            },
+    { NULL,                 NULL,                   NULL            },// SRC_OUT
+    { dstout_modeproc16_0,  NULL,                   NULL            },
+    { srcatop_modeproc16_0, srcatop_modeproc16_255, srcatop_modeproc16  },
+    { NULL,                 dstatop_modeproc16_255, NULL            },
+    { NULL,                 NULL,                   NULL            }, // XOR
+    { darken_modeproc16_0,  darken_modeproc16_255,  NULL            },
+    { lighten_modeproc16_0, lighten_modeproc16_255, NULL            },
+    { NULL,                 NULL,                   NULL            },//multiply
+    { NULL,                 NULL,                   NULL            }// screen
+};
+
+SkXfermodeProc16 SkPorterDuff::GetXfermodeProc16(Mode mode, SkColor srcColor) {
+    SkXfermodeProc16  proc16 = NULL;
+
+    if ((unsigned)mode < SkPorterDuff::kModeCount) {
+        const Proc16Rec& rec = gPorterDuffModeProcs16[mode];
+        
+        unsigned a = SkColorGetA(srcColor);
+
+        if (0 == a) {
+            proc16 = rec.fProc16_0;
+        } else if (255 == a) {
+            proc16 = rec.fProc16_255;
+        } else {
+            proc16 = rec.fProc16_General;
+        }
+    }
+    return proc16;
+}
+